At the end of the fall semester, seniors present to the physics department the results of their Phys 489: SYE Advanced Laboratory research projects. The abstracts for their research follow below:
The Effect of Non-Zero Absorption on Discrete Angle Radiative Transfer (DART) in Uniform and Multifractal Clouds - Mykael Goodsell-SooTho '14
This study analyzes the effect of adding a non-zero absorption probability into a pre-existing DART model that considered only conservative scattering (i.e. no absorption). We use sparse array techniques to exactly solve the radiance fields of a uniform density cloud as well as two clouds with densities defined by multifractal parameters. In all cases, we model our clouds as being subject to a uniform light source directed downward along the top of the cloud. We find that with non-zero absorption probabilities (defined by the coefficient a), the behavior of radiative transfer quantities fall into two categories depending on the value of a. In the low absorption regime (a = 0.00001 through a = 0.008), the mean downward radiance, vertical flux, and mean energy density versus pixel each mimic the qualitative behavior of the zero absorption case, but at lowered magnitudes. In the high absorption regime (a ≥ 0.01), all radiative transfer quantities fall of exponentially with pixel depth. We also find that in the high absorption regime, the albedo and transmission of each cloud are related to the absorption coefficient by well-defined power laws and exponential laws, respectively. As far as the authors can tell, study is the first of its kind in that the radiance fields of non-conservative DART-based systems are directly solved by sparse matrix inversion techniques.